Woo even flew to Kennebunkport, Maine, to photograph Barbara Bush with her beloved Sadie, an English springer spaniel.

The hardest photo shoot? That honor goes to Woo's longtime friend the musician Steve Miller, who has three dogs.

“We went to his house in Idaho,” Woo explains. “We stayed four days. I finally said, ‘Steve, come on. It's time to set everything up.' He has three herders, all rescue dogs, named Lady, Daisy and Maisey. They wouldn't sit still. They were running and jumping. It took forever.”